Very high power TEM of a section of a stage 2 embryo in vivo, (original magnification x30,000). Section is through an interblastomeric cell contact area. Notice the abundance of single vesicles close to the cell membranes (arrows).
From: Pereda and Croxatto, 1992. Reproduced with permission of the Annals, Academy of Medicine, Singapore.
Source: The Virtual Human Embryo.